6-K

Dated: August 7, 2025

/s/ Alexandra Roger

Name: Alexandra Roger

Title: Head of Legal Corporate & Finance

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of August 2025

Commission File Number: 001-31368

SANOFI

(Translation ofregistrant’s name into English)

46, avenue de la Grande Armée, 75017 Paris, FRANCE

(Address of principal executive offices)

Indicateby check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F.

Form 20-F ☒ Form 40-F ☐

In August 2025, Sanofi published the press release attached hereto as Exhibit 99.1 which is incorporatedherein by reference.

Exhibit Index


Exhibit No.		Description

Exhibit 99.1		Press Release dated August 6, 2025: Sanofi completes the acquisition of Vigil Neuroscience, Inc.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf bythe undersigned, thereunto duly authorized.

Exhibit 99.1


Press Release

Sanofi completes the acquisition of Vigil Neuroscience, Inc.

Paris, August 6, 2025. Sanofi announces the completion of its acquisition of Vigil Neuroscience, Inc. (“Vigil”). This acquisition strengthens Sanofi’s early-stage pipeline in neurologywith VG-3927, a novel, oral, small-molecule TREM2 agonist, which will be evaluated in a phase 2 clinical study in patients with Alzheimer’s disease. In addition, the acquisition of Vigil’spreclinical pipeline will further strengthen Sanofi’s research in various neurodegenerative diseases.

In June 2024, Sanofi made a$40 million strategic investment in Vigil that included the exclusive right of first negotiation for an exclusive license, grant, or transfer of rights to research, develop, manufacture, and commercializeVG-3927.

Under the terms of the acquisition agreement, Sanofi and Vigil have agreed to the following:

•

Sanofi acquired all outstanding common shares of Vigil for $8 per share in cash at closing, representing an equity valueof approximately $470 million (on a fully diluted basis)

•

In addition, Vigil’s shareholders received a non-transferrable contingentvalue right (CVR) per Vigil share, which entitles its holder to receive a deferred cash payment of $2, conditioned upon the first commercial sale of VG-3927.

VGL101, Vigil’s second clinical program, was not acquired by Sanofi. As previously communicated, the acquisition of Vigil is not expected to impactSanofi’s financial guidance for 2025.

About Sanofi

Sanofi is an R&D driven, AI-powered biopharma company committed to improving people’s lives anddelivering compelling growth. We apply our deep understanding of the immune system to invent medicines and vaccines that treat and protect millions of people around the world, with an innovative pipeline that could benefit millions more. Our team isguided by one purpose: we chase the miracles of science to improve people’s lives; this inspires us to drive progress and deliver positive impact for our people and the communities we serve, by addressing the most urgent healthcare,environmental, and societal challenges of our time.

Sanofi is listed on EURONEXT: SAN and NASDAQ: SNY

Media Relations

SandrineGuendoul | +33 6 25 09 14 25 | sandrine.guendoul@sanofi.com

Evan Berland | +1 215 432 0234 | evan.berland@sanofi.com

Léo Le Bourhis | +33 6 75 06 43 81 |leo.lebourhis@sanofi.com

VictorRouault | +33 6 70 93 71 40 | victor.rouault@sanofi.com

Timothy Gilbert | +1 516 521 2929 | timothy.gilbert@sanofi.com

Léa Ubaldi | +33 6 30 19 66 46 |lea.ubaldi@sanofi.com

Investor Relations

Thomas Kudsk Larsen | +44 7545 513 693 |thomas.larsen@sanofi.com

AlizéKaisserian | +33 6 47 04 12 11 | alize.kaisserian@sanofi.com

Felix Lauscher | +1 908 612 7239 | felix.lauscher@sanofi.com

Keita Browne | +1 781 249 1766 |keita.browne@sanofi.com

Nathalie Pham |+33 7 85 93 30 17 | nathalie.pham@sanofi.com

Tarik Elgoutni | +1 617 710 3587 | tarik.elgoutni@sanofi.com

Thibaud Châtelet | +33 6 80 80 89 90 |thibaud.chatelet@sanofi.com

Yun Li |+33 6 84 00 90 72 | yun.li3@sanofi.com



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Sanofi forward-looking statements

This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, as amended. Forward-lookingstatements are statements that are not historical facts. These statements include projections and estimates and their underlying assumptions, statements regarding plans, objectives, intentions, and expectations with respect to future financialresults, events, operations, services, product development and potential, and statements regarding future performance. Forward-looking statements are generally identified by the words “expects”, “anticipates”,“believes”, “intends”, “estimates”, “plans” and similar expressions. Although Sanofi’s management believes that the expectations reflected in such forward-looking statements are reasonable, investors arecautioned that forward-looking information and statements are subject to various risks and uncertainties, many of which are difficult to predict and generally beyond the control of Sanofi, that could cause actual results and developments to differmaterially from those expressed in, or implied or projected by, the forward-looking information and statements. These risks and uncertainties include among other things, the uncertainties inherent in research and development, future clinical dataand analysis, including post marketing, decisions by regulatory authorities, such as the FDA or the EMA, regarding whether and when to approve any drug, device or biological application that may be filed for any such product candidates as well astheir decisions regarding labelling and other matters that could affect the availability or commercial potential of such product candidates, the fact that product candidates if approved may not be commercially successful, the future approval andcommercial success of therapeutic alternatives, Sanofi’s ability to benefit from external growth opportunities, to complete related transactions and/or obtain regulatory clearances, risks associated with intellectual property and any relatedpending or future litigation and the ultimate outcome of such litigation, trends in exchange rates and prevailing interest rates, volatile economic and market conditions, cost containment initiatives and subsequent changes thereto, and theimpact that global crises may have on us, our customers, suppliers, vendors, and other business partners, and the financial condition of any one of them, as well as on our employees and on the global economy as a whole. The risks and uncertaintiesalso include the uncertainties discussed or identified in the public filings with the SEC and the AMF made by Sanofi, including those listed under “Risk Factors” and “Cautionary Statement Regarding Forward-Looking Statements” inSanofi’s annual report on Form 20-F for the year ended December 31, 2024. Other than as required by applicable law, Sanofi does not undertake any obligation to update or revise any forward-lookinginformation or statements.

All trademarks mentioned in this press release are the property of the Sanofi group.



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